Quartz crystal element using a thickness shear hexagonal quartz blank and method for manufacturing the same

Abstract

A quartz crystal element in which unwanted response is suppressed, comprising a thickness shear quartz blank such as an AT-cut type. An area where an amplitude of unwanted response may be strong can be eliminated from the quartz blank by forming the quartz blank into a substantially hexagon. Preferably, each pair of three pairs of opposite sides are mutually parallel and one of the pairs is parallel to the longest diagonal line of the quartz blank. For an AT-cut type of quartz crystal element, the direction of the longest diagonal line of the quartz blank is within the range of 28°±15° or 118°±15° from the Z' axis direction of the quartz blank, and the quartz blank is held at the ends of the longest diagonal line.

What is claimed is: 
     
       1. A quartz crystal element comprising: a substantially hexagonal quartz blank taken from an AT-cut quartz plate;   a pair of holding members for holding the quartz blank;   a first excitation electrode formed at a central portion of a first major surface of the quartz blank; and   a second excitation electrode formed at a central portion of a second major surface of the quartz blank;   wherein each pair of three pairs of opposite sides of the quartz blank are mutually parallel, one pair of the three pairs of the opposite sides are parallel to a longest diagonal line of the quartz blank, the direction of the longest diagonal line is within the range of 28°±15° from a Z' axis direction of the quartz blank, the holding members hold the quartz blank at holding ends which are the ends of the longest diagonal line, the first excitation electrode is led to one end of the longest diagonal line, and the second excitation electrode to the other end;   wherein at least one of the sides parallel to the longest diagonal line has the shape of arc.   
     
     
       2. The quartz crystal element according to claim 1, further comprising a base for retaining the holding members facing each other, wherein each of the holding members is made of a conductive material and has a penetrating hole, and the quartz blank is held by inserting the holding ends into the penetrating holes and applying a conductive adhesive around areas of the penetrating holes. 
     
     
       3. The quartz crystal element according to claim 1, wherein a length of the longest diagonal line of the quartz blank is up to 5 mm. 
     
     
       4. The quartz crystal element according to claim 1, wherein a length between a pair of the opposite sides parallel to the longest diagonal line is at least 10% to up to 60% of a length of the longest diagonal line. 
     
     
       5. The quartz crystal element according to claim 1, wherein each of the excitation electrodes has a shape substantially similar to that of the quartz blank. 
     
     
       6. A quartz crystal element comprising: a base;   a pair of lead wires implanted in the base;   holding members, each of which is fixed at an end of each of the lead wire, is made of a strip-shaped metal sheet, and has a longitudinal slot;   a substantially polygonal quartz blank;   a first excitation electrode formed at a central portion of a first major surface of the quartz blank; and   a second excitation electrode formed at a central portion of a second major surface of the quartz blank;   wherein the first excitation electrode is led to a first apex of the quartz blank, while the second excitation electrode is led to a second apex of the quartz blank;   a width of the slot at a lower end of the slot is narrower than a thickness of the quartz blank, and the slot is narrower in a lower portion thereof and broader in a higher portion thereof, and thus has a portion with a broader width than the thickness of the quartz blank; and   the quartz blank is held by inserting the first and the second apexes into the slots and then applying a conductive adhesive around the slots.   
     
     
       7. The quartz crystal element according to claim 6, wherein the quartz blank has a substantially hexagonal shape in which ends of a longest diagonal line of the quartz blank are the first and the second apexes. 
     
     
       8. The quartz crystal element according to claim 7, wherein a direction of the longest diagonal line is within a range of 28°±15° from a direction of a Z' axis.